Modern farming practices in North America require the application of fertilizer in order to maximize crop yields and, in turn, maximize profits. Currently, approximately 40% of this fertilizer is applied as anhydrous ammonia (NH3) since it is the most cost effective per unit of nitrogen. However, despite this cost advantage, the use of NH3 has not changed significantly in the past few decades due to safety issues and the extra labor involved in a applying the NH3. Historically, conventional knife injection applicators have been used to apply the NH3 in the ground. These applicators generally tow a 1000-1500gallon NH3 nurse tank. Multiple NH3 wagons are used to support each applicator. When the tank borne by the wagon being towed by the applicator becomes empty, it is exchanged with a wagon bearing a full tank. A tender truck hooks up to the wagon bearing the empty tank in the field and transports it to a central fill station and then transports the wagon with the newly filled tank back to the field for the applicator to use. The current tank change operation is a multi-step process which requires the operator to physically dismount the tractor, put on NH3 safety garb and/or, equipment and walk back to the just emptied tank to manually bleed and disconnect the tank. Typically, conventional applicators have to change tanks every 1 ½ hours and the process can take up to 15minutes with the operator, being exposed to a small amount of NH3 vapor, hence the requirement for the safety garb and/or equipment. This manual tank change operation is inconvenient to the operator and reduces the overall productivity of the applicator.
It is a trend in farm equipment of various types to make units larger in order to more quickly cover the ground. However, an applicator which has the capability to apply NH3 at nearly twice the speed of a conventional applicator would require the tanks to be exchanged nearly twice as often, or once every 45minutes. Employing the conventional manual change regimen, the down time involved in exchanging empty with full tanks would result in the large unit operating only at 75% efficiency.
The problems to be addressed then are those of reducing the amount of time required for exchanging empty with full tanks of NH3 while reducing exposure of the operator to NH3.